Parasites Cycle - Lecture on June 5th-10th

Hookworms (Ancylostoma)

Life Cycle:

1. Eggs in feces

2. Rhabditiform larva hatches

3. Filariform Larva

4. Filariform larva penetrates the skin

5. Male and female worms mate in the lower intestinal tract

Infection Process:

• Rhabditiform larvae: Never infectious

• Filariform larvae: Always infectious

• Penetrates skin through the bloodstream

• Attaches to capillaries and sucks blood

Trichinella Spiralis

Transmission:

• Primarily through undercooked or raw pork

• Alternative source: Bear meat

Life cycle:

• Larval stage (Nurse cell) remains in the body and travels through the bloodstream.

• The larval stage enters the muscle tissue, eventually breaking it down.

• Nurse cell: larval stage in muscle tissue

Health risk:

• It can be potentially fatal if it reaches the heart muscle tissue or diaphragm muscles.

Dracunculus medinensis (Guinea Worm)

Transmission:

• Ingesting undercooked crustaceans or fish.

• The pregnant female worm creates a boil on the skin’s surface when she lays her eggs.

• When the boil comes in contact with water, it bursts, releasing the larval stages.

• This parasite potentially inspired the medical symbol.

Wuchereria bancrofti

Transmission:

• Carried by mosquito

Infection Process:

• Mosquito bite introduces larvae

• Adults migrate to lymph nodes

• The adult worm block the lymph drainage, this causes elephantiasis (massive swelling) usually in the legs or testicles.

Onchocerca volvulus

Transmission:

• Carried by black flies

• These flies leave a bump on the skin (nodule) which then becomes an adult and make babies that eventually go to the chamber behind the eyes.

Blindness cause:

• What causes blindness is the immune system reaction to larval stage behind the eye.

Why are these flies called “River Blindness?”

• Black Flies are found in the river since they like to lay eggs in places with high oxygen.

Dirofilaria (Dog Heartworm)

Transmission:

• Mosquito-brone

Infection Process:

• Larvae enters dog’s heart chambers

• Can potentially infect humans (rare)

• It can clog heart chambers and can be fatal to dogs.

Enterobius vermicularis (Pinworm)

Life Cycle:

• Eggs ingested

• Larvae hatch in intestinal tract

• Females migrate to anal region to lay eggs

Diagnostic test:

• Scotch tape test

• If one family member is infected, entire family needs medication.

Trichuris trichiura (Whipworm)

Morphology:

• Thin, whip-like shape

• Males are curly

• Females are straight

Life cycle:

• Eggs are passed in feces

• Picked up by the next host through ingestion

• Think “neck” attaches to intestinal wall

• Egg characteristics: Has two polar plugs

Ascaris lumbricoides

• Largest human roundworm

• Can cause intestinal blockages

Life cycle:

• Eggs in dirt

• Ingested by humans

• Mature in lower intestines

Egg characteristics:

• Rugged appearance

• Rough, textured surface

Strongyloides stercoralis

• Two potential life cycles: Parasitic and free-living

Larval stages:

• Rhabditiform: Non-infectious

• Filariform: Infectious

Infection process:

• Penetrates the skin

• Enters bloodstream

• Travels through the lungs

  • coughed up and swallowed

• Reaches the intestinal tract

Distinctive feature:

• Both males and females are outside

• Once they’re in the human body, only females are present.